The present invention relates to a brake pad for a disc brake and, in particular, to a brake pad for a commercial vehicle disc brake.
A generic-type brake pad is known from DE 40 20 287 A1. The construction, which is shown and described there, has proved itself to work properly in practice. In this case, the brake pad holder is formed so that the brake pad spring forms a grip so that the sub-assembly, which includes the brake pad spring and the brake pad, is very easy to handle, for example for installation or removal.
For fixing the pad retaining spring, lugs, which are provided with undercuts and penetrate into slot-shaped recesses in the pad retaining spring, are formed on the pad carrier plate and fit behind the undercuts in the process so that a positive lock is formed. As a result, the pad retaining spring is retained in the radial direction so that an automatic disengagement in the relaxed or partially relaxed position is excluded.
Since for fixing the pad retaining spring only two connecting points are provided, which are arranged at a distance from each other, the pad retaining spring is held in the middle when being used as a handle or grip so that the pad retaining spring functions in the sense of a carrier, which is clamped at both ends, with the tendency of bending it by a corresponding degree.
As a result of this deformation, the spring characteristic of the pad retaining spring can possibly change, which can act disadvantageously during functioning.
The production of the undercut lugs of the pad carrier plate is basically only possible by way of a mechanical machining, for example by impressing, stamping or the like. This applies equally to the formation of the slot-shaped recesses of the pad retaining spring, which can also only be formed by corresponding mechanical machining.
The invention further develops the above-mentioned brake pad so as to optimize its functional load.
By way of the invention, the effect is achieved of the pad retaining spring being clamped in a load-transmitting manner, especially in the load region, as a result of which bending of the pad retaining spring is avoided since the lever arm, which has been effective up to now, is now no longer present.
According to an especially advantageous development, a hood, by which the pad retaining spring is fastened on the pad carrier plate according to the invention, is preferably arranged in the middle region of the pad retaining spring where the force distribution is especially optimum and is rigidly connected there to the pad retaining spring, especially in a positive-locking or material-bonding manner, so that it does not become lost and cannot inadvertently spring off from the pad carrier plate.
Also, the connecting region on the pad carrier plate is preferably located approximately in its middle region, wherein a middle 30% of the pad carrier plate and of the pad retaining spring, which face each other, in each case, especially preferably the middle 10%, are to be understood as the middle region.
The positive lock between the hood and the pad carrier plate can be formed so that removal of the pad retaining spring from the pad carrier plate is only possible by destruction of the connection, which comprises the pad retaining spring and the hood. Consequently, it is ensured that when replacing the brake pad only the sub-assembly including the brake pad and brake retaining spring can be exchanged. That is to say, reuse of a previously used pad retaining spring is excluded, as a result of which an improvement of the operating safety naturally ensues.
According to an advantageous development of the invention, the pad carrier plate and the hood are provided with positive-locking parts, which correspond to each other and allow an adequate radial deflection of the pad retaining spring. For this purpose, the pad carrier plate can have radially extending recesses in which associated teeth of the hood engage with a locking effect.
For producing the installation unit comprising the brake pad and brake pad spring, fixing of the hood and, as a result, of the pad retaining spring on the pad carrier plate, is carried out by a locking tongue which, after seating of the hood on the pad carrier plate, is deformed and in an unloaded end position of the pad retaining spring abuts against a stop of the pad carrier plate.
A lug of the pad carrier plate is associated with each of the two spring legs of the pad retaining spring, which extend on both sides of the hood, and against which abuts the respective spring leg. As a result, twisting of the pad retaining spring is effectively prevented. These lugs are preferably cast on if the pad carrier plate is formed as a cast part, wherein the arrangement of the lugs can be undertaken on one side or on both sides. Apart from that, by way of the positive-locking connection of the hood to the pad carrier plate, a problem-free compensation of casting tolerances is possible without an additional machining of the pad carrier plate being necessary.
According to a further aspect of the invention, the pad retaining spring, at least inside the covering region of the hood, is provided with a more progressive spring characteristic than in the adjacent spring legs.
Because of the at least two different spring excursions, significant advantages ensue in the spring characteristic during operation compared with a pad retaining spring according to the prior art.
During “normal operation” of the disc brake, the relatively long spring legs are first effective with a low spring force, as corresponds, inter alia, to the legal requirements.
During running operation, in which as a result of heavy vibrations relatively loud rattling noises of the brake pad occur, which certainly do not signify a functional limitation but which are considered as extremely annoying, a shorter spring arm becomes effective with a relatively large spring force, as a result of which the brake pad is prevented from lifting from the brake carrier, which otherwise leads to the rattling noises.
The symmetrical supporting of the pad retaining spring by way of the hood also contributes towards minimizing of these noises, as a result of which a one-sided lifting of the brake pad from the brake carrier is prevented or reduced.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.